MUDShell
mudshell.com
Forums for coding help, egg drops, admins, social forums, coders, and general discussion.
The MUD Connector
mudconnect.com
Covers various topics including administrative ethics and area building.
Top MUD Sites
topmudsites.com
Various MUD related discussions from coding to legal issues.
Gammon Software Solutions Forum
gammon.com.au
Support site for MUSHclient and PennMUSH. Also provides MUD coding help for beginners.